Forward Fairing, Aircraft Structure, Flap Support Structure and Aircraft

This application claims the benefit of European Patent Application Number 24182165.1 filed on Jun. 14, 2024, the entire disclosure of which is incorporated herein by way of reference.

The invention relates to a forward fairing for an aircraft, an aircraft structure with the forward fairing, a flap support structure with the aircraft structure and an aircraft with the aircraft structure.

An aircraft fairing is a structure whose primary function is to produce a smooth outline and reduce aerodynamic drag. A fairing can serve as a cover for gaps and spaces between parts of an aircraft in order to reduce aerodynamic drag and interference drag and to also improve appearance. The fairing is commonly non-structural and attached to a further structure of the aircraft.

U.S. Pat. No. 9,227,722 B2 describes a flap support structure for an aircraft wing which supports an aerodynamic fairing. The flap support structure has a flap support beam including an aerodynamic fairing and a drive unit including a universal support structure which rotatably receives a drive shaft connected to a drive arm for moving the trailing edge flap. The universal support structure also forms part of the flap support beam and supports the aerodynamic fairing.

It is desirable to provide a fairing that can be easily attached to a further structure of the aircraft.

The invention provides a forward fairing for an aircraft. The forward fairing comprises a fairing shell and an attachment device. The aft attachment device comprises a protrusion that is integrally formed with the fairing shell and a spigot that is coupled to the protrusion.

The spigot is used to mount the shell onto a support structure of the aircraft. An integrated protrusion in the fairing shell is provided. This reduces the number of parts that have to be assembled. Additionally, a fairing with a smoother outer surface can be provided as an additional fastening between the protrusion and the shell can be avoided. Thus, aerodynamic drag can be reduced.

For example, the protrusion and fairing shell may be integrally formed using molding fabrication methods or by additive manufacturing methods, such as three-dimensional printing, in which the desired structure of the shell and protrusion is successively built-up layer by layer. Thus, a joint between two separate parts, i.e., between the protrusion and shell, is avoided.

The protrusion can also be considered to be a bracket.

In an embodiment, the protrusion has a substantially cylindrical form with a base and an end face. The base of the protrusion protrudes from an inner surface of the fairing shell. The upward part of the protrusion that protrudes from the inner surface may extend substantially perpendicularly to the inner surface or at an inclined angle to the inner surface.

In an embodiment, the base of the protrusion comprises a skirt that merges into the inner surface of the fairing shell. The skirt provides a smooth transition between the upward part of the protrusion and the inner surface of the shell. This arrangement distributes loads more homogeneously.

In an embodiment, the spigot has a shaft, a neck and a head. The head is laterally larger than the shaft and the neck and the neck is laterally smaller than the shaft and the head. In an embodiment, the shaft, the neck and the head of the spigot are each substantially cylindrical and the head protrudes radially from the neck.

In an embodiment, the protrusion comprises a recess formed in its end face. The recess comprises an inner thread and the shaft of the spigot comprises an external thread. This enables the spigot to be coupled to the protrusion by screwing the spigot into the protrusion. The shaft of the spigot is engaged with the protrusion by the interlocked outer thread and inner thread.

In alternative embodiment, the spigot is integral with the protrusion and comprises a neck and a head protruding from the end face of the protrusion. This embodiment has the advantage that the number of parts that are to be assembled is further reduced.

The forward fairing may have a forward end and an aft end and the attachment device may be located towards the aft end. The forward fairing may be elongate and have a longitudinal axis that extends between the forward end and the aft end and the attachment device may be located towards the aft end. The forward fairing may further comprise a reinforcement structure, for example ribs and/or stringers that are attached to the inner surface of the shell.

The fairing shell and the integral protrusion may be formed of a fiber reinforced plastic, for example carbon fiber reinforced plastic. These materials provide high strength at a low weight. Furthermore, these materials can be used in an additive manufacturing process to form the shell and integrated protrusion.

The invention also provides an aircraft structure which comprises the forward fairing according to any one of the embodiments described herein and a support structure comprising a key slot.

In an embodiment, the key slot is formed in a U-shaped bracket that is attached to the support structure. The U-shaped bracket may be separate from the support structure and attached to the support structure by one or more additional fastenings or may be integral with the support structure.

In an embodiment, the key slot is elongated and comprises a first enlarged aperture at a first end and a second enlarged aperture at a second end opposing the first end. The first enlarged aperture has a greater diameter than the second enlarged aperture.

In an embodiment, the key slot is located such that the fairing shell is engageable with the support structure by forward and aft movement of the fairing shell relative to the support structure.

In an embodiment, the key slot is located such that the larger first enlarged aperture is positioned forward of the smaller second enlarged aperture with respect to the aircraft. This enables the forward fairing to be fitted to the support structure by a movement in the direction of the aft of the aircraft.

In an embodiment, the head of the spigot is insertable in the first enlarged aperture of the key slot is, therefore, laterally smaller than the first enlarged aperture. The head of the spigot is laterally larger than the second enlarged aperture such that the head is supported by the bracket surface surrounding the second enlarged aperture of the key slot in the mounted position of the fairing on the support structure.

In an embodiment, the neck is laterally smaller than the second enlarged aperture and is located in the second enlarged aperture of the key slot in the mounted position of the fairing on the support structure.

The invention also provides a flap support structure comprising the aircraft structure according to any one of the embodiments described herein.

The invention also provides an aircraft wing comprising the aircraft structure according to any one of the embodiments described herein.

The invention also provides an aircraft comprising the aircraft structure according to any one of the embodiments described herein.

To summarize, the protrusion (bracket part) on the fairing side is integrated into the fairing shell and thus results in a reduction in the number of parts and simplified assembly. Instead of manufacturing several parts and assembling them with fasteners the fairing shell and the bracket part are integral. For example, additive manufacturing techniques, such as three-dimensional printing techniques may be used to produce the fairing shell and protrusion in one manufacturing step.

The aft attachment of the forward fairing keeps the forward fairing in place in direction of flight. The aft part of the forward fairing is also able to move in chord direction. The rotation canter is in the forward connection of the forward fairing. Once the spigot is in place in the smaller part of the key hole, the fairing can rotate round the axial axis of the spigot in the integral protrusion.

Because of the integral design of the fairing shell and protrusion, fewer parts are needed. This reduces the cost of part and of assembly. The weight is reduced as there is no overlap in assembly areas and no flanges sized by minimum edge distance of fastener holes are used. There is also a reduction in lead time as no assembly time is needed in the planning process. A further advantage is that a smoother outer surface can be provided, also for a double curved surface, since the outer surface is not interrupted, e.g., by the flat heads of the countersunk fasteners. At the same time, kinematic movement remains.

depicts a side view of an aircraftcomprising a fuselage, two opposing wingsand under-wing mounted engines. Each winghas moveable trailing edge flapsmounted to the wing fixed trailing edge. The flapsare supported by and moveable with respect to the fixed portion of the wingby flap support structures. Whilst the aircraft shown inis a commercial transport aircraft, the invention is applicable to a wide variety of aircraft types. It is also applicable to aircraft with engines mounted other than under the wing, e.g. aft mounted engines.

The flap support structuregenerally includes a flap support beam, a forward fairingand a moveable aft fairing. The aft fairingis fixed with respect to the flapand moves with the flapbetween a retracted position adjacent the wing fixed trailing edge and one or more extended positions.

The forward fairingis attached to the flap support beamby way of the attachment structureillustrated in, wherebydepicts a perspective view,a cross-sectional view of the forward fairingand attachment structureandillustrates an enlarged view of the attachment structureof.

The forward fairingcomprises a shellextending along a longitudinal axis between a forward endand an aft end. The attachment structurecomprises a protrusionthat is integrally formed with the shell, in particular with the inner surfaceof the shelland a spigotthat is coupled to the protrusion. The protrusionmay also be referred to as a bracket.

The protrusionprotrudes from the inner surfaceof the shell. In an embodiment, the protrusionmay extend substantially (i.e., +/−10%) perpendicularly to the inner surface. Alternatively, the protrusion may extend at an inclined angle, i.e. less than 90°, to the inner surface. The dimensions of the protrusionand its angle of protrusion from the inner surfacemay be selected depending on the position of the protrusionon the support structureof the aircraftto which the fairingis to be connected.

The protrusionis substantially cylindrical and comprises a recessin its end surfacewhich comprises an internal thread. The base of the protrusioncomprises a skirtwhich merges into the inner surfaceof the shellto create a smooth transition between the outer surface of the protrusionand the inner surfaceof the shell. The skirtforms a radial transition that is concave.

In some embodiments, the attachment structuremay further include a support sectionwhich also protrudes from the inner surfaceof the shelland which abuts an outer side wall of the substantially cylindrical protrusion. The support sectionmay have a substantially triangular footprint and extend from the forward to aft direction with a decreasing height so as to provide support for the protrusionduring mounting of the forward fairingonto the flap support beam. The support sectionmay be integral with the shelland may also be integral with the protrusion.

The spigotcomprises a substantially cylindrical body or shaftwith an external thread so that the shaftcan be screwed into the recessof the protrusionto attach the spigotto the protrusionand to the shellof the forward fairing. The spigotcomprises a headand a neckthat is located between the shaftand the head. The headis laterally larger than the shaftand the neckand the neckis laterally smaller than the shaftand the head. The shaft, the neckand the headare each substantially cylindrical and the headprotrudes radially from the neck. The neckhas a smaller diameter than that of the shaftand the headhas a larger diameter than that of the neckand of the shaft.

The flap support beamcomprises a support structureto which the shellis to be attached. This support structurecomprises a U-shaped bracketcomprising a key slotalso known as a keyhole slot which comprises an elongate aperture. The key slotcomprises a first enlarged apertureat a first end and a second enlarged apertureat a second end that opposes the first end. The first and second enlarged apertures,are each substantially circular. The second enlarged aperturehas a smaller diameter than the first enlarged aperture.

The first and second enlarged apertures,and the headand neckof the spigotare sized such that the headcan pass through the first enlarged aperturebut not through the second enlarged apertureand such that the neckcan pass through the second enlarged aperture. Thus, the shellcan be attached to the support structureby inserting the headof the spigotthrough the first enlarged aperture, moving the headand the shellfrom the first end towards the second end of the elongated key slotinto the second enlarged apertureso that the neckis located in the second enlarged aperture. In this mounted position, the neckis supported by the bracket surface around the second enlarged apertureso that the shelland fairingare mounted on the support structure.

The elongate key slothas a longitudinal axis. This enables the aft of the shellto be attached to the support structureby moving the shellrelative to the key slotin one direction. In an embodiment, the longitudinal axis of the key slotextends in the direction from the front to the rear of the aircraft. Thus, the shellcan be attached to the support structureby moving the shellrelative to the key slotin the direction from the front to the rear of the aircraft.

The spigotis moveable in the key slotbetween a first position in the first enlarged apertureand a second position in the second reduced diameter aperture. In the first position, the spigotand shellis able to be removed from the support structure, from example perpendicularly away from the U-shaped bracket. In the second position, the spigotand shellis secured to the support structure. The key slothas a first part (enlarged aperture) into which the spigotcan be inserted/removed, and a second part (enlarged aperture) in which the spigotcannot be inserted or removed.

The forward fairingis rotatable about the spigot, i.e. it rotate around the z axis. This rotational movement allows aft attachment in the chord direction. The chord direction is the direction between the leading edge and trailing edge of the wing.

In an alternative embodiment, the spigotis integral with the protrusion. In this embodiment, the neckand headprotrude from the end faceof the bracket. In this alternative embodiment, the attachment structurehas a similar outer appearance to that shown in.

A fairingwith an integrated protrusionis provided. Additive manufacturing techniques, such as three-dimensional printing techniques may be used to produce the fairing shelland protrusionin one manufacturing step. The number of parts is reduced and assembly simplified since, instead of assembling several parts with additional fasteners, the fairing shelland the protrusionare integral. Thus, the fairing shellcan be mounted onto the support structurein a simpler movement by inserting the spigot headinto the larger apertureof the key slotand sliding the shelland spigotinto the smaller apertureof the key slot.

While at least one exemplary embodiment of the present invention(s) is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the exemplary embodiment(s). In addition, in this disclosure, the terms “comprise” or “comprising” do not exclude other elements or steps, the terms “a” or “one” do not exclude a plural number, and the term “or” means either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority.